This proposal requests funds to purchase a Rigaku RU-300 X-ray generator with focusing mirrors, an R-AXIS IV image plate system, and an X-stream low temperature system to improve the existing X-ray diffraction facility at the University of Pennsylvania School of Medicine. The original facility was developed for a single crystallographer and his collaborators. In the past three years, the School of Medicine has hired five new faculty who will all be using X-ray crystallography to address important biological problems in macromolecular structure, function, and design. In addition to hiring new faculty, the University and the School of Medicine have invested over one million dollars to renovate 7000 square feet of laboratory space for structural biology, of which 3000 square feet will be specifically dedicated to X-ray crystallography. This new space will house the existing equipment, as well as the new equipment proposed in this grant. The instrumentation will be jointly managed by the P.I. (Dr. Mitch Lewis) and the three co- P.I.'s (Drs. Greg Van Duyne, Pat Loll, and Hillary Nelson), all of whom have established active crystallography programs. A Ph.D. level scientist will be hired during the summer of 1998 to supervise installation of the equipment in the new space, as well as to perform ongoing equipment maintenance, assist users, and train new users. This scientist will also be available to assist other Medical School scientists that are not X-ray diffraction specialists but who wish to initiate crystallographic projects. In support of this request for shared instrumentation funds, the Department of Biochemistry and Biophysics along with the Department of Pharmacology have agreed to provide funds to support the new X-ray facility manager in the Medical School.